High pressure decorative laminates containing an air-laid web of fibers and filler and method of producing same

ABSTRACT

The invention relates to high pressure decorative laminates containing an air-laid web of fibers, filler and resin as a core and to a method of preparing such a decorative laminate from an assembly comprising said substrate and a thermosetting resin impregnated decor sheet.

BACKGROUND OF THE INVENTION

The production of cores comprising cellulosic fibrous sheets and athermosetting resin composition useful in supporting decorative layersin the formation of high pressure decorative thermoset laminates is wellknown. Conventionally, said cores comprise a plurality, i.e. about 2-10,of paper core sheets impregnated with a liquid thermosetting resincomposition, said core sheets being prepared by treating a web of paper,prepared by a wet-laying process, with a solution or dispersion of athermosetting resin composition in a volatile solvent, drying saidtreated web to reduce the volatile matter content to a desired level andcutting said treated, dried paper web into sheets of the requireddimensions.

In order to provide satisfactory handling and usage properties in saidlaminates, they are conventionally produced in thicknesses of from about0.5 mm to about 2.0 mm, this thickness range being achieved primarily bysuperimposing the required number of said paper core sheets. While it isrecognized that it would clearly be advantageous to use a single sheetto provide the core for the laminate, problems of manufacture andprocessing associated with the production and resin-impregnation ofwet-laid paper sheets having a basis weight significantly greater thanabout 250 gsm (grams per square meter) and a thickness of greater thanabout 0.20 mm has prevented their production.

Further, for environmental and energy conservation reasons, it isconsidered desirable to obviate the drying stage necessary withconventionally produced resin composition treated paper cores. Attemptsmade in the past to avoid this drying step by providing a wet-laid papercontaining a thermo-setting resin composition in solid particulate formas a sheet of the laminate core and formed during the paper makingprocess from an aqueous slurry comprising the paper fibers and theparticulate resin failed because of problems arising from the propensityof the liquid phase to convey the resin particles through the formingwire.

Wet-laid papers, while generally producing high pressure decorativelaminates of excellent properties, have a propensity to causestress-cracking of laminates under conditions of low relative humidity.Therefore, conventional high pressure decorative laminates, after aperiod of time well within their expected life-times, oftimes undergo amarked deterioration in their aesthetic appearance and utility.Conventional high pressure decorative laminates therefore have notalways proven useful in areas where low relative humidity is a prevalentcondition especially where the laminates are first subjected tomodification such as by notching, cutting or other treatment wherebysharp corners are cut into their cross-section.

Wet-laid core papers also exhibit a variation in at least some of theirphysical properties depending upon whether the properties are measuredin the direction of travel of the machine wire upon which the paper wasformed, or transversely of it. This variation in properties is due tothe non-random orientation of the fibers in the paper due to thealignment of fiber caused by the flow of the liquid phase onto andthrough the wire and by surface tension effects. Laminates produced fromcores comprising said wet-laid papers also exhibit this directiondependent variation in at least some of their physical properties andalthough this is not generally disadvantageous, there are someapplications where a laminate exhibiting less variation in physicalproperties according to the direction of measurement is preferred.

Recently, it has been found that high pressure decorative laminateproduced from a thermosetting resin containing fibrous cellulosic corewherein the disadvantages of laminates made by conventional processesare overcome or diminished may be produced by using, as the core, anair-laid web comprising both cellulosic fibers and a thermosettingresin.

High pressure decorative laminates made from air-laid webs exhibit atoughness superior to laminates which contain, as their core, aplurality of thermosetting resin impregnated Kraft paper sheets. Thistoughness is evidenced by the laminates' increased resistance tostress-cracking. Furthermore, such high pressure decorative laminatescontaining an air-laid core also exhibit substantially equivalentuniform strength and dimensional properties regardless of the machinedirection from which the measurement is taken.

Air-laid fibrous webs are prepared by disintegrating fibrous, cellulosicmaterial into its component fibers, transporting the fibers to aforaminous moving web-forming surface and depositing the fibers thereonto form a layer with the aid of suction applied to the under side of theweb-forming surface. The fibrous, cellulosic material is disintegratedinto its component fibers by a machine such as a hammermill or discrefiner and the individual fibers are transported to the forming surfacein an air-stream. Binder material is applied to or admixed with thefibers as a particulate solid or as a liquid spray and the web depositedtherefrom is then consolidated between nip rollers. When the binder isadded as a solid to the air-fiber stream, it may be introduced into thehammermill or thereafter, but before deposition on the forming surface.Additionally, when the binder is used as a spray, the sprayed fibers maythereafter be dried and introduced as such into the forming apparatus.

A known apparatus for forming substrates by air-laying cellulosic fiberscomprises: (i) an air-swept hammermill wherein cellulosic material isdefibrated into its component fibers in an air-stream, (ii) ductingwhereby the fiber containing air-stream is conveyed to a distributor,(iii) a distributor such as disclosed in U.S. Pat. No. 3,581,706,comprising a housing having a perforated planar bottom wall and sidewalls, one or more impellers mounted to rotate about an axissubstantially perpendicular to the bottom wall a short distance aboveand in non-contacting relationship with the upper surface of said bottomwall, inlet means for the fiber containing air-stream to enter thedistributor, outlet means whereby fibrous material may be recycled tothe hammermill and, optionally, a plate member located above saidimpellers and extending inwardly from the side walls of the housing soas to form a partition between a lower part and an upper part of saidhousing, said distributor being positioned so that the bottom wall iscooperatively located above the upper surface of (iv) a moving,foraminous belt upon the upper surface of which the cellulosic fibersare deposited to form a layer with the aid of (v) means for applyingsuction to the under surface of said belt and (vi) means for compactingthe so-deposited cellulosic fiber layer, see U.S. Pat. Nos. 2,698,271and 4,014,635.

When apparatus of the type described above is used in the production ofan air-laid cellulosic fibrous layer, there are a large number ofvariables that must be controlled in order that optimum formation of thelayer occurs. These variables include the input rate of the cellulosicmaterial to the hammermill, the speed of rotation of the impellers andspeed of travel of the belt and the degree of compaction applied. Whenpreparing a core adapted for use in the production of high pressuredecorative laminates, the thermosetting resin must be uniformlydistributed throughout the deposited layer and there must be sufficientof the resin present to provide the desired properties to the heat andpressure consolidated laminate. In the production of such high pressuredecorative laminates, the resin content of the core lies in the rangefrom about 10% to about 40% by weight, preferably from about 25% toabout 30%, based on the total weight of the core.

Additionally, for the formation of an air-laid core having the desireduniformity of composition and basis weight and comprising fibers andthermosetting resin, such as by means of an apparatus of the typedescribed above, it is preferable to operate under conditions such thatthe air has a relative humidity within the range of about 40% to 80%,preferably about 50% to 70% in order to prevent deposition problemswhich may arise in that at too high a humidity, clogging of the ductingand screen may occur, while at too low a humidity, problems may arisedue to static electrical charges on the fibers.

In the production of decorative laminates from either wet-laid orair-laid cores various forms of waste material are produced in thefinishing operations necessary in connection with manufacture of thesedecorative laminates. One of the operations performed upon the finishedlaminates i.e. those recovered upon removal thereof from the laminatingpress, consists of trimming all the peripheral edges of each laminate inorder to remove "flash", i.e. any portion of the laminate peripherywhich is not fully consolidated during lamination. This material is verybrittle and detracts from the overall appearance of the laminate. Asecond operation performed upon the finished laminates is the sanding ofthe back or reverse side thereof so as to provide a good surface forbonding of the laminate to a suitable underlayment via the use of acontact adhesive. Also, the finished laminates are oftimes cut to sizein order to supply the ultimate consumer with a variety of lengths andwidths for fabrication into commercial articles, resulting in cuttingdust.

The waste or offal produced by the trimming, sanding and cuttingoperations is a major concern to laminate manufacturers because duringthese finishing operations as much as 14% of the weight of the finallaminate may be removed. Thus, the waste created can cause significanthandling, disposal, environmental and energy concerns.

Additionally, other forms of waste accrue. That is to say, during thecourse of producing the components which go into the ultimate laminatesi.e. the overlay sheets, the decor sheets etc., objectionable orsub-quality material may be produced which is not suitable for producinga quality laminate and therefore must be discarded. Additionally, otherwaste material may be generated during the laminating operation per sein the form of imperfect laminates, i.e. laminates with physicaldeficiencies, surface imperfections and the like.

If a use for these above-described waste materials could be found suchthat even a portion of the material usually discarded, burned orotherwise disposed of could be reused, a long felt need in thelaminating industry would be solved.

SUMMARY OF THE INVENTION

It has now been found that high pressure decorative laminates producedfrom a thermosetting resin containing fibrous cellulosic core may beproduced by using as the core, an air-laid web comprising (a) cellulosicfibers, (b) from about 1% to about 20% of a pulverized filler and (c) athermosetting resin.

The novel high pressure decorative laminates of the present inventionexhibit a toughness superior to laminates produced conventionally whichcontain, as their core, a plurality of thermosetting resin impregnatedkraft paper sheets and also substantially retain the uniform strengthand dimensional properties of laminates produced from air-laid webswhich do not contain the recycled waste filler.

Furthermore, the disclosed method of recycling the plant waste materialsinto a useful, viable laminate core component, reduces the need for thedisposal of these materials by other more costly means. Thus, the methodprovides for a significant pollution control in the making of laminates.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS

According to the instant invention, there is provided a heat andpressure consolidated decorative laminate comprising, in superimposedrelationship:

(I) a thermoset resin containing, monostichous core of air-laid,randomly oriented, substantially non-hydrogen bonded cellulosic fibershaving an average length of 0.5 to 2.5 mm, said core being from about0.25 mm to about 2.25 mm thick, containing from about 10% to about 40%by weight, of resin, based on the total weight of fiber and resin in Iand from about 1% to about 20%, by weight, based on the total weight ofsaid fiber, of a pulverized filler;

(II) a thermoset resin impregnated cellulosic decor sheet andoptionally,

(III) a thermoset resin impregnated alpha-cellulosic overlay sheet.

In accordance with the instant invention, the method for preparing thethermoset, high pressure, decorative laminates comprises:

(1) forming a laminate assembly comprising, in super-imposedrelationship:

(A) a monostichous, air-laid core of randomly oriented fibers of 0.5-2.5mm average length, containing from about 10-40% of a thermosetting resinand from about 1% to about 20%, by weight, same basis as above, of apulverized filler and of sufficient thickness to provide, whenconsolidated, from about 0.25 mm to about 2.25 mm in thickness to theresultant laminate,

(B) a thermosetting resin impregnated decor sheet and optionally,

(C) a thermosetting resin impregnated alpha-cellulose overlay sheet; and

(2) consolidating said assembly to a unitary thermoset laminatestructure by the application of heat and pressure thereto.

The thermosetting resin containing monostichous core of randomlyoriented, substantially non-hydrogen bonded cellulosic fibers is formedusing an apparatus of the type described above, by:

(a) feeding fibrous, cellulosic material to a defibrator such as anair-swept hammermill and defibrating the material therein to providecellulosic fibers of an average length of about 0.5 to 2.5, preferablyabout 0.75 to 2.0 mm, in the presence of humidified air, the relativehumidity of which ranges from about 40% to about 80% to thereby form anair-fiber stream;

(b) incorporating into said air-fiber stream from about 10% to about 40%by weight, of a thermosetting resin, said weight being based on thetotal weight of resin and fiber, and from about 1 to about 20% byweight, based on the total weight of fiber, of a pulverized filler, tothereby form an air-fiber-filler-resin stream;

(c) passing said air-fiber-filler-resin stream to a distributor;

(d) agitating said stream within the distributor by impeller means;

(e) causing said stream to pass through the perforated bottom wall ofthe distributor;

(f) depositing the fibers, filler and resin onto a moving foraminousbelt to form a layer having a thickness of from about 5 mm to about 100mm, preferably about 10 mm to 80 mm by the operation of the suctionmeans, and

(g) pre-consolidating the deposited layer to a thickness of from about0.5 mm to about 10.0 mm, preferably about 1.0 to about 8.0 mm.

The fibrous, cellulosic material employed may comprise any material suchas chemical, semi-chemical or mechanical paper pulp, cardboard and wastepaper and the like, provided that after defibration in the hammermill itcomprises fibers of an average length of 0.5 mm to 2.5 mm. Althoughfibers produced from wood are preferred, fibers produced from straw,grass, bagasse, cotton or synthetics, may be used alone or in admixture.If the cellulosic material feed is in bulk form, then it is preferred touse a balebreaker or similar equipment to partially disintegrate thematerial before it is fed to the hammermill.

The air fed to the hammermill may be humidified to the above-specifiedextent either internally or externally of the core forming apparatus.Thus, the apparatus may be situated in a room, the air in which ishumidified to the required degree and drawn through the apparatus at therequired rate. Alternatively, the air may be drawn into the apparatusand there humidified such as by steam or water spray means to therequired level. It is preferred to humidify the air internally of theapparatus as such allows for quicker adjustment of the humidity than ispossible with external humidification and further allows the room air tobe controlled independently so as to provide more amenable workingconditions.

The said thermosetting resin may comprise any thermosetting resin whichprovides the required properties in the core prepared therefrom. Theresin may comprise, for example, a phenol-formaldehyde resin, amelamine-formaldehyde resin, a polyester resin or an epoxy resin andsaid resins may comprise known extenders, if desired. It is preferred toemploy a particulate, thermosetting resin and even more preferred toemploy a phenol-formaldehyde resin. Such a particulate resin may beprepared by forming a solid, thermosetting resin in bulk or lump formand then grinding or crushing to provide the desired particle size or,more preferably, it may be prepared in particulate form by knownemulsion or suspension condensation techniques. The mean particle sizeof the thermosetting resin should range from about 20 microns to about200 microns, preferably from about 50 to 150 microns.

The filler material used herein may comprise any of the waste or offalmaterials discussed above associated with the production of decorativelaminates. Thus, the filler material may constitute laminate sandingdust, laminate cutting dust, laminate edge trimmings (flash), laminatepieces, resin impregnated papers and the like. The filler must be ofsuch a size that it will not create a distorted surface in the laminateproduced from the core containing the same. It is essential that theparticle size thereof accordingly be adjusted such as by pulverizationto no larger than about 200 microns with from about 50 to 150 micronsbeing preferred.

The thermosetting resin and the pulverized filler may be incorporatedinto the air-fiber stream by any suitable means and at any suitableposition. Thus the resin and/or filler may be introduced into thehammermill, into the ducting between the hammermill and the distributor,or into the distributor. Suitable introductory means are known andinclude spraying means, gate-valves, vibratory- and screw-feeders etc.It is preferred to employ screw feeders which employ a positive feedprinciple and can be controlled more precisely to give the feed rate ofresin and/or filler desired.

The air-laid layer may be pre-consolidated between platens or niprollers as may be most convenient and the pre-consolidating means may beheated or cooled, if desired. If they are heated, then thepre-consolidation must be such that while there may be some conversionof a minor amount of the thermosetting resin to the thermoset form, asubstantial proportion of the resin is still in the thermosetting formafter the pre-consolidation operation. The air-laid layer, beforepre-consolidation, must be of such a thickness that after heat andpressure consolidation during laminate formation the core of saidlaminate will range in thickness from about 0.25 mm to about 2.25 mm.Air-laid webs deposited on the belt, which may be constructed of metalor other material such as plastic, cloth etc., are deposited at thepre-consolidation thickness specified above.

The thermosetting resin impregnated decor sheet employed in the presentinvention may comprise any of those decor sheets known to provide thedecorative surface on a decorative laminate and includes decorativewoven or non-woven fabrics, colored or printed paper sheets, woodveneer, cork, and the like. The resin may be of any of those known foruse in the production of thermoset laminates but it is preferred to usethose `noble` thermosetting resins by which is meant those resins whichshow no appreciable darkening or color change on conversion from thethermosetting to the thermoset state.

When a decorative woven or non-woven fabric sheet or a printed papersheet is employed, it is preferred to use, in addition thereto, asurfacing overlay sheet known for use in the production of conventionalthermoset laminates. More especially, it is preferred to use a lightweight, high quality, unfilled, alpha-cellulose paper sheet impregnatedwith the same kind of thermosetting resin composition as used toimpregnate the decorative sheet and, still more preferably, an overlaysheet impregnated with a thermosetting melamine-formaldehyde resin maybe employed.

The optional overlay sheet may comprise any of those overlay sheetsknown to provide a protective, abrasion-resultant surface to decorativelaminates. Preferably, these overlay sheets comprise alpha-cellulosepaper which is impregnated with a noble thermoset resin, preferablymelamine/formaldehyde, and which become transparent upon heat andpressure consolidation of the laminate assembly.

The heat and pressure consolidation is suitably carried out using thatmachinery, equipment, press-plates, temperature, pressure and press-timeused for preparing decorative thermo-set laminates from the conventionalimpregnated kraft paper core layers. Pressures ranging from about 700 toabout 1400 psi and temperatures ranging from about 120° to 150° C.

The laminate assembly is consolidated by heat and pressure so that inthe high pressure thermoset laminate the thickness of the air-laidsubstrate is reduced by a factor of about two to about ten. Moreespecially, it is preferred to effect the heat and pressureconsolidation so that in the product laminate, the substrate has athickness of from about 0.25 mm to about 2.25 mm, as mentioned above.

Further, while it is preferred to prepare laminates comprising a singlecore made in accordance with the invention, a single thermosetting resinimpregnated decor sheet and, optionally, a thermosetting resinimpregnated alpha-cellulose overlay sheet, the invention is not solimited and also encompasses laminates comprising a core produced frommore than one monostichous, non-hydrogen bonded, air-laid web, the noblethermosetting resin impregnated decor sheet and, optionally, the noblethermosetting resin impregnated overlay sheet.

The following examples are set forth for purposes of illustration onlyand are not to be construed as limitations on the present inventionexcept as set forth in the appended claims. All parts and percentagesare by weight unless otherwise specified.

EXAMPLE A

Defibrated kraft linerboard fibers are mixed with powderedphenol/formaldehyde resin and formed onto a stationary screen with theaid of suction applied to the underside of a screen. The resultantfiber-resin layer has a thickness of 46 mm, a density of 0.035 g/c.c., abasis weight of 1600 gsm and a fiber to resin weight ratio of 3:1. Thedeposited fiber-resin layer is preconsolidated, at a pressure of 2300psi, to a thickness of 2.25 mm.

After conditioning the compacted monostichous, fiber-resin core layer at60% relative humidity for 24 hours, a decorative thermoset resinouslaminate assembly is formed comprising:

(a) the above monostichous core layer,

(b) a printed decor paper impregnated with a thermosettingmelamine/formaldehyde resin to a resin content of about 40% and,

(c) an alpha-cellulose overlay sheet impregnated with a thermosettingmelamine/formaldehyde resin to a resin content of about 60%.

After positioning between separating sheets, the assembly is heat andpressure consolidated at 1400 psi and 145° C. to a unitary thermosetdecorative laminate with a thickness of 1.12 mm.

EXAMPLES Sanding Dust and Trim Saw Waste

Sanding dust and trim saw wastes in two particle size ranges areevaluated, a coarse material with a particle size of from 0.033" to0.008" and a fine material with most of the material less than 0.003".The coarse materials are collected directly from sanders or trim saws.Large slabs and pieces are removed by screening through a 20 mesh perinch sieve and only the portion which passes through the sieve is used.The accepted material has the texture of coarse sand. Characteristics ofthe fine or pulverized filler materials are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    CHARACTERISTICS OF PULVERIZED FILLERS                                                                   TRIM                                                                    SANDING                                                                             SAW                                                 ANALYSIS            DUST  WASTE                                               __________________________________________________________________________    2000 microns        0.0   0.0                                                 710 microns         4.8   0.1                                                 212 microns         39.3  7.1                                                 150 microns         16.3  11.6                                                Smaller than 150 microns                                                                          36.9  78.7                                                % VOLATILE          4.03  4.75                                                WATER SOLUBLE PHENOL Mg/g                                                                         2.2   9.4                                                 WATER SOLUBLE PHENOLIC Mg/g                                                                       14.2  35.0                                                ASH CONTENT, %      1.01  6.16                                                ACID INSOLUBLE ASH, %                                                                             0.39  5.20                                                __________________________________________________________________________

Cores are made using normal procedures but either 5, 10, or 20% of thefiber is replaced with the respective filler material. Each core has 30%resin therein. The cores are pressed with melamine/formaldehyde resinimpregnated print and trans sheets at 145° C. and 1400 psi for 20minutes. One laminate is pressed without print and trans sheets for coremachinability testing. Core only laminates are made using otheravailable fiber sources to determine machinability between differenttype of fibers.

Results in Tables 2, 3 and 4 show that physical properties of thelaminates with fillers are equivalent to those of the control withoutfillers. Water absorption and thickness swell are equivalent butdimensional change increased slightly at higher filler contents.

The addition of the coarse materials, Table 2, results in a somewhatrough appearance in the print surface if larger amounts of filler areused. The rough appearance is caused by the inability of the hardparticles to compress and the resulting high pressure in these areas. Nosurface roughness is evident when using the rough materials at lesseramounts.

Treated Decorative Print and Transparent Overlay

Sheet stock of melamine/formaldehyde resin impregnated decorative printand transparent overlay is disintegrated in a 140 mm hammermill. Thedisintegrated materials are then mixed with fiber, cores made andlaminate pressed the same as for the sanding dust evaluation. At the 20%filler addition level, the quantity of resin added is reduced tocompensate for the resins in the treated sheets.

When the treated print and trans are disintegrated in the hammermill, nosticking is evident within the mill. Some dusting, however, isexperienced during the grinding. Table 5 shows that the physicalproperties of the laminates with different filler levels remainessentially unchanged. Water absorption and thickness swell decrease asthe filler addition levels increase. At 20% filler addition, acceptabletest levels are achieved after reductions of resin addition of 5 and 10%for print and trans addition, respectively. The difference inmachinability between samples indicate that some increase in tool wearmay be experienced when adding, decorative print but not by addingtransparent overlay.

                                      TABLE 2                                     __________________________________________________________________________    EVALUATION OF COARSE.sup.(1) SANDING DUST & TRIM SAW WASTE                    Example No. 1.sup.(C)                                                                          2    3    4    5    6    7    8    9    10                   __________________________________________________________________________    Phenolic Resin (Solid)                                                        Added, %    30   30   30   30   30   30   30   30   30   30                   Retained, % (in core)                                                                     24.9 23.8 22.1 26.1 24.2 23.1 24.5 21.9 --   2.62                 Fiber (Linerboard)                                                            %           100  95   90   80   60   95   90   80   90   80                   Filler                                                                        Sanding Dust, %                                                                           0    5    10   20   40   0    0    0    5    10                   Trim Saw Waste, %                                                                         0    0    0    0    0    5    10   20   5    10                   Laminate Properties,                                                          Sanded                                                                        Basis Weight, gms                                                                         1653 1732 1780 1713 1612 1727 1713 1581 1692 1696                 Density, kg/m.sup.3                                                                       146  144  144  144  136  142  143  139  136  142                  Water Absorption, %                                                                       6.69 5.80 6.14 5.91 8.44 6.37 6.86 9.12 6.38 7.93                 Thickness Swell, %                                                                        7.40 5.34 5.44 4.91 5.14 6.27 5.86 6.62 6.43 6.80                 Dimensional Change                                                            High Humidity, %                                                                          0.321                                                                              0.343                                                                              0.350                                                                              0.356                                                                              0.407                                                                              0.305                                                                              0.324                                                                              0.325                                                                              0.343                                                                              0.350                Low Humidity, %                                                                           0.786                                                                              0.783                                                                              0.822                                                                              0.876                                                                              0.924                                                                              0.770                                                                              0.808                                                                              0.862                                                                              0.815                                                                              0.818                Gross, %    1.107                                                                              1.126                                                                              1.172                                                                              1.232                                                                              1.331                                                                              1.075                                                                              1.132                                                                              1.187                                                                              1.158                                                                              1.168                Tensile, mPa                                                                              86.7 82.1 81.7 87.5 80.8 86.1 78.3 84.1 82.4 79.9                 Modulus, mkPa                                                                             4.78 4.60 4.80 4.71 4.42 4.70 4.83 4.65 4.52 4.58                 Core Machinability.sup.(2)                                                                6.0  6.0  6.0  6.0  6.0  6.0  6.0  6.0  6.0  6.0                  Stress Crack, Hrs.                                                                        92+  92+  92+  92+  15   92+  92+  48+  92+  92+                  Surface Appearance.sup.(3)                                                                0    0    1    2    2    1    2    2    2    2                    __________________________________________________________________________     .sup.(1) Particle Size Average 50-200 microns                                 .sup.(2) 3.0 to 8.0  Typical of nonaggressive kraft laminate.                 .sup.(3) 0 = Smooth, 1 = Slight irregularities, 2 = Very rough (orange        peel appearance).                                                             .sup.(C) Comparative                                                     

                                      TABLE 3                                     __________________________________________________________________________    EVALUATION OF PULVERIZED SANDING DUST                                         EXAMPLE No.  11.sup.(C)                                                                         12   13   14   15.sup.(C)                                                                         16   17   18.sup.(C)                                                                         19   20                  __________________________________________________________________________    Phenolic                                                                      Resin (Solid)                                                                 Added, %     30   30   30   30   30   30   30   30   30   30                  Retained, % (in core)                                                                      20.4 23.4 23.6 21.4 30.0 28.0 29.0 22.0 21.0 24.2                Fiber                                                                         Type         Linerboard          Saturating          Linerboard               %            100  95   90   80   100  90   80   100  90   80                  Filler                                                                        Sanding Dust, %                                                                            0    5    10   20   0    10   20   0    10   20                  Laminate Properties,                                                          Sanded                                                                        Basis Weight, gms                                                                          1671 1759 1600 1624 1551 1583 1541 1619 1604 1596                Density, kg/m.sup.3                                                                        144  145  140  142  145  138  137  142  144  143                 Thickness, Swell, %                                                                        6.14 4.98 5.87 5.85                                              Water Absorption, %                                                                        7.67 6.96 7.38 7.43                                              Dimensional Change,                                                           Length                                                                        High Humidity, %                                                                           0.510                                                                              0.484                                                                              0.521                                                                              0.534                                             Low Humidity, %                                                                            0.519                                                                              0.532                                                                              0.539                                                                              0.546                                             Gross, %     1.029                                                                              1.016                                                                              1.060                                                                               1.080                                                                             PHYSICAL PROPERTIES NOT TESTED               Dimensional Change,                                                           Cross                                                                         High Humidity, %                                                                           0.539                                                                              0.554                                                                              0.570                                                                              0.550                                             Low Humidity, %                                                                            0.602                                                                              0.617                                                                              0.622                                                                              0.626                                             Gross, %     1.141                                                                              1.171                                                                              1.192                                                                              1.176                                             Tensile, mPa 85.6 76.0 90.9 79.8                                              Modulus, mkPa                                                                              4.80 4.65 5.08 4.71                                              Core Machinability.sup.(1)                                                                 12.0 12.0 10.5 12.0 1.0  7.0  7.0  4.0  6.0  6.0                 Ash, %       1.67 --   1.72 --                                                Surface Appearance.sup.(2)                                                                 0    0    0    0                                                 __________________________________________________________________________     .sup.(1) 3.0 to 8.0  Typical of nonaggressive kraft laminate.                 .sup.(2) 0  smooth, 1 = Slight irregularities, 3 = Very Rough.                .sup.(C) Comparative                                                     

                                      TABLE 4                                     __________________________________________________________________________    EVALUATION OF PULVERIZED TRIM SAW WASTE                                       EXAMPLE No.  21.sup.(C)                                                                         22   23   24   25.sup.(C)                                                                         26   27   28.sup.(C)                                                                         29   30                  __________________________________________________________________________    Phenolic                                                                      Resin (Solid)                                                                 Added, %     30   30   30   30   30   30   30   30   30   30                  Retained, % (in core)                                                                      20.4 19.0 23.9 22.9 30.0 30   32.0 22.0 24.0 25.2                Fiber                                                                         Type         Linerboard          Saturating     Linerboard                    %            100  95   90   80   100  90   80   100  90   80                  Filler                                                                        Trim Saw Waste, %                                                                          0    5    10   20   0    10   20   0    10   20                  Laminate Properties,                                                          Sanded                                                                        Basis Weight, gms                                                                          1671 1743 1604 1695 1551 1551 1570 1619 1619 1642                Density, kg/m.sup.3                                                                        144  145  144  144  145  139  144  142  139  140                 Thickness Swell, %                                                                         6.14 6.14 5.62 5.33                                              Water Absorption, %                                                                        7.67 6.93 6.81 6.37                                              Dimensional Change,                                                           Length                                                                        High Humidity, %                                                                           0.510                                                                              0.486                                                                              0.534                                                                              0.544                                             Low Density, %                                                                             0.519                                                                              0.522                                                                              0.533                                                                              0.558                                                                              PHYSICAL PROPERTIES NOT TESTED               Gross, %     1.029                                                                              1.008                                                                              1.067                                                                              1.102                                             Dimensional Change,                                                           Cross                                                                         High Humidity, %                                                                           0.539                                                                              0.548                                                                              0.555                                                                              0.573                                             Low Humidity. %                                                                            0.602                                                                              0.584                                                                              0.637                                                                              0.629                                             Gross, %     1.141                                                                              1.132                                                                              1.192                                                                              1.202                                             Tensile, mPa 85.6 72.6 74.9 82.8                                              Modulus, mkPa                                                                              4.80 4.75 4.56 4.54                                              Core Machinability.sup.(1)                                                                 12.0 14.5 13.0 14.0 1.0  3.0  2.0  4.0  4.0  4.0                 Ash, %       1.67 --   2.40 --                                                Surface Appearance.sup.(2)                                                                 0    0    0    0                                                 __________________________________________________________________________     .sup.(1) 3.0 to 8.0  Typical of nonaggressive kraft laminate.                 .sup.(2) 0 = Smooth, 1 = Slight irregularities, 2 = very rough.               .sup.(C) Comparative                                                     

                                      TABLE 5                                     __________________________________________________________________________    EVALUATION OF TREATED DECORATIVE PRINT & TRANSPARENT OVERLAY                  EXAMPLE No.   31   32   33   34   35   36   37   38                           __________________________________________________________________________    Phenolic                                                                      Resin (Solid)                                                                 Added, %      30   30   30   30   30   30   35   25                           Retained, % (in core)                                                                       22.2 26.5 25.8 27.8 25.7 28.4 32.1 23.7                         Fiber (Linerboard)                                                            %             95   90   80   80   95   90   80   80                           Filler                                                                        Print, %      5    10   20   20   0    0    0    0                            Trans, %      0    0    0    0    5    10   20   20                           Laminate Properties, Sanded                                                   Basis Weight, gms                                                                           1562 1582 1573 1568 1551 1536 1563 1582                         Density, kg/m.sup.3                                                                         145  143  145  147  144  143  144  144                          Thickness Swell, %                                                                          6.36 6.37 5.30 6.91 7.16 5.91 5.69 6.92                         Water Absorption, %                                                                         8.11 7.68 6.90 7.90 8.72 8.30 7.77 8.76                         Dimensional Change                                                            High Humidity, %                                                                            0.466                                                                              0.435                                                                              0.428                                                                              0.468                                                                              0.602                                                                              0.587                                                                              0.588                                                                              0.480                        Low Humidity, %                                                                             0.514                                                                              0.532                                                                              0.493                                                                              0.516                                                                              0.548                                                                              0.562                                                                              0.564                                                                              0.546                        Gross, %      0.980                                                                              0.967                                                                              0.921                                                                              0.984                                                                              1.150                                                                              1.149                                                                              1.152                                                                              1.026                        Tensile, Length, mPa                                                                        85.8 82.0 85.5 83.2 80.8 76.6 88.7 90.3                         Cross, mPa    77.6 78.9 74.2 83.2 78.7 79.3 72.0 72.2                         Modulus, Length, mkPa                                                                       4.70 4.51 4.82 4.73 4.62 4.33 4.53 4.78                         Cross, mkPa   4.62 4.55 4.50 4.64 4.26 4.37 4.41 4.66                         Core Machinability                                                                          7.0  6.0  8.0  9.0  6.5  7.0  5.0  6.0                          __________________________________________________________________________

EXAMPLE 39

When the procedure of Example 3 is repeated except that a continuouscommercial apparatus is employed, similar results are achieved.

The apparatus employed essentially comprises: an electrically driven,air-swept hammermill connected by suitable ducting to a distributor;screw-feed means arranged to feed particulate thermosetting resin intothe ducting between the hammermill and the distributor; a distributorcomprising a housing having side-walls and end-walls and a perforatedplanar bottom-wall and side walls, impeller means mounted to rotateabout an axis substantially perpendicular to the bottom-wall a shortdistance above and in non-contacting relationship with the upper surfaceof said bottom-wall, inlet means for the fiber-containing stream, outletmeans whereby fibrous materials are recycled to the hammermill, a platemember located above said impellers and extending inwardly from theside-walls so as to form a partition between the lower part and an upperpart of the housing, said distributor being positioned so that thebottom-wall is located above and co-operates with a moving foraminousbelt and said side-walls and end-walls being provided with means torestrict passage of air between their lower extremeties and said belt; amoving, foraminous metal mesh belt positioned above and co-operatingwith suction means positioned therebelow and a pair of metal compactionrollers mounted so as to act in nip relationship on said belt and adeposited layer thereon.

Soft wood sulphate kraft having a kappa number of 32 is fed to theair-swept hammermill where it is defibrated to provide cellulosic fibershaving an average fiber length of about 1 mm. Air, humidified to 70%relative humidity by steam injecting means, is fed to the hammermill ata rate of 38.6 cubic meters per kilogram of fibers to produce anair-fiber stream. Solid particulate thermosetting phenolic resin havinga mean particle size of about 25 microns and laminate sanding dust ofless than 100 microns are incorporated by the screw-feeder means intothe air-fiber stream to provide an air-fiber-filler resin stream whereinthe ratio of resin to fiber was about 1 part to 3 parts, by weight. Theair-fiber-filler-resin stream is then passed to the distributor, whenceby action of the suction means and the impeller means, the stream iscaused to pass through the perforated bottom-wall thereof and to depositas a fiber-filler-resin layer having a basis weight of 1560 gsm adensity of 0.029 g/cc and a thickness of 54 mm upon the foraminous beltwhich is moving at a speed of 0.8 meters/minute.

The belt and the deposited fiber-resin layer are then passed through thenip of the compaction rollers which exert thereon a line pressure ofabout 45 Kg/cm and preconsolidation thereof. The material emergent fromthe nip is separated from the belt as a thermo-setting phenolic resincontaining monostichous substrate of randomly oriented substantiallynon-hydrogen bonded cellulosic fibers of about 3.6 mm in thicknesscontaining 33%, by weight, of the resin.

The core formed is used to prepare a high pressure thermoset decorativelaminate assembly by arranging in superimposed relationship:

(a) the monostichous substrate;

(b) a printed, paper decor sheet impregnated with a thermosettingmelamine-formaldehyde resin to a resin content of about 40%; and

(c) an alpha cellulose overlay sheet impregnated with a thermosettingmelamine-formaldehyde resin to a resin content of about 50%.

The assembly thus formed is positioned between separating sheets andthen consolidated to a unitary thermoset decorative laminate 1.2 mmthick by heating at 145° C. under a pressure of 1400 psi in an hydraulicpress. After cooling and removing the laminate from the press, thethermoset decorative laminate so obtained is substantially identical inappearance and properties as set forth in Example 3.

EXAMPLE 40

Using the apparatus of the type described in Example 39,semi-thermochemical softwood pulp is fed to the air-swept hammermill andthere defibrated to an average fiber length of about 1.5 mm in thepresence of a stream of humidified air at a relative humidity of about70% flowing at a rate of 40.9 cubic meters of air per kilogram of fiber.

The resultant air-fiber stream leaving the mill is passed via suitableducting to the distributor and a particulate thermosetting resin of meanparticle size of about 20 microns and fine laminate cutting dust of15-150 microns are incorporated into the air-fiber stream at a weightratio of fiber to resin of 2.5 to 1 by means of a screw feeder adaptedto feed material into the ducting. The air-fiber-filler resin isagitated in the distributor by the impeller means and caused by thesuction means to pass through the perforated bottom-wall and deposit,upon the foraminous belt moving at 0.8 m/minute a fiber-filler- resinlayer having a basis weight of 1260 gsm, a thickness of about 30 mm anda density of 0.042 g/cc. The deposited layer and the moving belt arethen passed through the nip of the compaction rollers operating at aline loading of 45 Kg/cm and the deposited layer emerging from the nipis separated from the wire to provide a thermo-setting resin containingmonostichous substrate of randomly oriented, substantially non-hydrogenbonded, cellulosic fibers having a thickness of 6 mm.

A decorative thermosetting plastics laminate assembly is formedcomprising, in superimposed relationship:

(a) the monostichous substrate formed above;

(b) a printed decor paper impregnated with a thermo-settingmelamine-formaldehyde resin to a resin content of about 40%; and

(c) an alpha-cellulose overlay sheet impregnated with a thermosettingmelamine-formaldehyde resin to a resin content of about 60%; and afterpositioning between separating sheets the assembly is consolidated to aunitary thermoset decorative laminate comprising:

(a) a monostichous core layer, about 0.9 mm thick of randomly oriented,substantially non-hydrogen bonded cellulosic fibers, containing about28% of thermoset phenolic resin and 12% filler cutting dust;

(b) a decorative layer comprising the thermoset melamine-formaldehyderesin impregnated printed decor paper sheet; and

(c) a wear surface layer comprising the thermoset melamine-formaldehyderesin impregnated alpha cellulose overlay sheet.

The resultant laminate has excellent properties and surface appearance.

EXAMPLE 41

The procedure of Example 19 is again followed except that the overlay isomitted. Again, the high pressure decorative laminate produced from themonostichous substrate is of excellent mechanical strength anddimensional properties.

EXAMPLE 42

The procedure of Example 37 is again followed except that the air-laidweb contains 24.9% of a 50/50 mixture of a first Novalac phenolic resincontaining hexamethylenediamine and a second resole phenolic resin. Thefinished high pressure decorative laminate has excellent properties.

EXAMPLE 43

The procedure of Example 31 is again followed except that theair-deposited fibers are composed of 95% linerboard and 5% fiberboardmechanical pulp. The properties of the resultant high pressuredecorative laminate are excellent.

EXAMPLE 44

When the procedure of Example 32 is again followed, except that thefibers are first sprayed with the phenolic resin and dried beforedepositing them on the foraminous belt, and the resultant monostichoussubstrate is employed in the manufacture of a laminate substantiallyequivalent results are achieved.

We claim:
 1. A heat and pressure consolidated decorative laminatecomprising, in superimposed relationship,(a) a monostichous layer ofrandomly oriented, substantially non-hydrogen bonded, air-laidcellulosic fibers of from about 0.25 mm to 2.25 mm thickness andcontaining from about 10 to 40%, by weight, based on the total weight offiber and resin in (a), of a thermoset resin and from about 1% to about20%, by weight, based on the total weight of said fiber, of pulverized,particulate filler having a particle size no larger than about 200microns, and(b) a thermoset resin impregnated cellulosic print sheet. 2.A laminate in accordance with claim 1 containing, positioned atop said(b), (c) a thermoset resin impregnated α-cellulose, transparent overlaysheet.
 3. A laminate in accordance with claim 1 wherein said fibers arecellulosic kraft fibers.
 4. A laminate in accordance with claim 1wherein said thermoset resin in (a) is a phenolic resin.
 5. A laminateaccording to claim 1 wherein said filler is selected from the groupconsisting essentially of (1) laminate sander dust, (2) laminate cuttingdust, (3) laminate edge trimming, (4) pulverized laminate and (5) resinimpregnated paper.